Insights / Your guide to electric vehicle batteries

Your guide to electric vehicle batteries

5th January 2022

What are EV batteries made of, how do they work, how long do they last, and what can we do with them after their useful lives?

The power in an electric vehicle (EV) comes from something not very different to the battery in your mobile phone. Both are lithium-ion battery packs. But while your phone only has one power pack, the batteries in an EV are made up of thousands of individual lithium-ion cells.

What are lithium-ion cells made from?

They’re made from a number of substances including cobalt, lithium, manganese and nickel.

Why choose lithium-ion batteries for EVs?

Lithium-ion cells are now an economic battery technology, making them a suitable choice for EVs. They have fallen in price dramatically over the last 30 years, and are predicted to continue to get cheaper still.

How does the battery generate electricity?

In a lithium-ion cell, lithium ions flow from one part of the battery (the anode) through a liquid called the electrolyte to another part of the battery (the cathode). This forces electrons to flow through an outside circuit. (During charging this process happens in reverse.)

The electricity that is generated is then turned into mechanical energy in the EV’s electric motor. This occurs because of the interaction between the motor’s magnetic field and the electric current flowing through the motor’s wire winding. This then generates force which turns the motor’s drive shaft.

A charging cycle is one full charge and discharge of a battery.

Each completed charging cycle very gradually reduces the amount of power the batteries can store. This means that after every charging cycle, an EV can drive for very slightly less distance on a single charge. It also means it will take very slightly less time to charge the battery. This process normally takes many years.

What’s the lifetime of an EV battery?

Individual batteries are different, but there’s general agreement that EV batteries have a lifetime of between 10 and 20 years. That’s much longer than the typical manufacturer’s warranty. Manufacturers create ‘excess capacity’, to allow the batteries to continue effective charging cycles even as they age.

Is there any way to increase the lifetime of EV batteries?

Batteries are ‘buffered’, so they can’t use absolutely all of the charge they contain. This effectively reduces the number of complete charging cycles they go through, so they can last longer. EVs are also fitted with special equipment designed to keep batteries cool, which can help extend their life, too.

Does battery size affect range?

The larger the size – measured in Kilowatt hours (KWh) – of an EV’s battery, the greater its charging capacity, and the longer its range on a single charge. And of course, the vast majority of EV journeys are for very much shorter distances than their total range. This is still true for fleet drivers, as our telemetry shows.

What happens to EV batteries after their working lifetime?

Batteries are reused in other functions – storing power for use in the electricity network for instance, or in people’s homes. This demand is expected to continue to grow. When batteries can’t be used to store power, they’re recycled. Currently, around 50% of the materials used in batteries can be re-used in this way. However, manufacturers are already working on ways to make battery recycling more effective.

How sustainable are EV batteries?

Batteries are made from lithium ion. There are emissions associated with the mining of this material, and with the production of the battery itself.

However, the batteries have long lifecycles, and the most efficient models take just two to three years of driving to save the amount of carbon emitted in producing their batteries.

Since batteries can also be used in domestic settings beyond its life in a car. Some estimates place this secondary lifespan at between 10 and 15 years, which means they can continue to payback emissions for longer.

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